Haha. This is interesting, because I'm actually reading a fanfic where Charlie and Sue get married. I think that its quite possible that something like that could happen, though. I mean, they are both lonely now, and they need someone.
I was looking through this thread, and some were asking where it was said that Billy was jealous of Charlie. That can be found here
, during the Breaking Dawn tour (the part is at about 7:30).